fix: No tests for transpiler stack-depth validation (#619)

Add TypeScript unit test suite for the Push3 transpiler using Node's
built-in test runner (node:test) with tsx. 47 tests across 12 suites
covering parser, stack underflow/overflow, EXEC.IF balanced/unbalanced/
nested branching, arithmetic, boolean ops, name binding, and integration.

Update CI to run `npm test` (which now includes unit tests + existing
bash tests) and scope transpiler-tests step to only trigger on changes
to tools/push3-transpiler/**.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.woodpecker/ci.yml

@@ -65,6 +65,11 @@ steps:
 
   - name: transpiler-tests
     image: registry.niovi.voyage/harb/node-ci:latest
+    when:
+      - event: pull_request
+        path:
+          include:
+            - tools/push3-transpiler/**
     commands:
       - |
         bash -c '
@@ -73,8 +78,7 @@ steps:
           cd tools/push3-transpiler
           npm install --silent
           npm run build
-          bash test_inject_extraction.sh
-          bash test_transpiler_clamping.sh
+          npm test
         '
 
   - name: single-package-manager